Portable electric heat gun

ABSTRACT

A portable heat gun especially applicable for shrinking of heatshrinkable polyethylene tubings. A brushless self-lubricating electric motor is positioned within a hollow pistol grip shaped housing of high impact plastic, in line with an air intake orifice in the rear of the housing. The motor carries a fan to push intake air past a heating wire wound round a stiff, flat, refractory card maintained within the inner stainless steel tube of the two co-axial tubes set in the housing and giving the heat gun the appearance of a pistol, and then through an exhaust orifice. The tubes and card are held in place by a set of screws and by associated spacer elements. Air may be passed between the tubes to provide thermal insulation. A three-way switch permits fan operation with or without heating. Support means on the housing cooperate with the handle to provide a tripod support for holding the tubes vertical.

United States Patent Pattison 1541 PORTABLE LECTRIC HEAT GUN [5 8] Field of Search UNITED STATES PATENTS 2,859,327 1 H1958 146111111511 1. ..219/366, 1,346,471 7/1920 Slater ....2l9/362 1,603,117 10/1926 K111111161 ..34/96 2,678,376 5/1954 Lockwood. ..219/366 x 3,209,988 10/1965 FOX 61 111. ..219/370 ux 3,21 1,890 10/1965 0111166 ..219/370 FOREIGN PATENTS OR APPLlCAfllONS 1,246,218 8/1967 Germany ..219/373 Primary Examiner-A. Bartis AttorneyFrancis J. Thornton and Irwin A. Shaw [57] ABSTRACT A portable heat gun especially applicable for shrinking of heat-shrinkable polyethylene tubings. A brushless selflubricating electric motor is positioned within a hollow pistol grip shaped housing of high impact plastic, in line with an air intake orifice in the rear of the housing. The motor carries a fan to push intake air past a heating wire wound round a stiff, flat, refractory card maintained within the inner stainless steel tube of the two co-axial tubes set in the housing and giving the heat gun the appearance of a pistol, and then through an exhaust orifice. The tubes and card are held in place by a set of screws and by associated spacer elements. Air may be passed between the tubes to provide thermal insulation. A three-way switch permits fan operation with or without heating Support means on the housing cooperate with the handle to provide a tripod support for holding the tubes vertical.

: 5 Claims, 6 Drawing Figures PATENTEBJUH 6 I972 SHEET 1 BF 2 INVENTOR RICHARD A.PAT ISON a ATTORNEY FIG. 4

1 PORTABLE ELECTRIC HEAT GUN BACKGROUND OF THE INVENTION There exists in the prior art numerous examples of electric heat guns. All of these heat guns have significant drawbacks when considered for the shrinking of heat shrinkable polyethylene tubings.

Other guns which have been designed for use with heat shrink and source applications, have been found to be so large and unweildy that the user becomes tired and his labor arduous when the gun is used for any extended period of time.

The present invention was designed to overcome the disadvantages of those guns found in the prior art and was designed to be easy to use, without maintenance or lubrication and to provide long, trouble-free service in either intermittent or continuous operation. Additionally, the present invention was constructed to withstand the normal in-use wear and tear encountered with any high qua1ity,.electrically powered hand tool. The uncomplicated arrangement of parts and wiring in the unit allows for quick and easy repair.

The motor in the unit is a self-lubricating brushless type and no oiling or replacement of brushes is necessary. The external portions of the unit are constructed from high impact plastic and high strength alloyed steel and the heating element is designed to withstand normal impacts and physical shocks.

SUMMARY OF THE INVENTION A modern, compact, reliable, low-cost, portable heat gun for use in heat shrink applications comprising a body of high impact plastic, containing an electric motor, a blower fan and a heating element'disposed within a pair of coaxial tubes, maintained in line with said blower to cause air to pass over theheating element and to become h ated to approximately 1,000 Fahrenheit, suitable for the excitation of memory within anirradiated or otherwise treated plastic element. A

simple system of screws and spacer elements holds the tubes in the gun and maintains the relative position of the tubes with respect to each other and to a stiff, flat card about which a heating wire is wound. Two handed manipulation of a plastic element is made possible by support means on the gun housing which form two parts of a tripod, the handle providing the third part, to hold the tubes vertical. 1

DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION OF THE INVENTION FIG. 1 provides an over-all view of the present invention which is seen to comprise a compact, reliable, low cost, easily repairable heat gun generally having a pistol configuration. The gun itself has two basic sections, i.e. the body composed of insulating material and the nozzle 11 which is metallic.

The body 10 is shell separable into two complementary halves 14 and 14a along line 13. Half 14a is the mirror image of half 14 shown in detail in FIG. 2 which shows a view of the gun cut along the line 13. Shells l4 and 140 are molded and hollow and serve to enclose a motor 15, a fan 16, a switch 18 and to hold in a fixed position nozzle 11. The shells 14 are preferably made of a high impact plastic such as is sold under the trade mark Noryl Grade 85-], by the General Electric Company.

The shell halves 14 and 14a are held together by a plurality of bolts (not shown) which pass through points 20, 21, 22 and 23. Points 21 and 22 are located in flanges 211 and 221 which extend out from the main body of the shell. Point 20 is located in the handle and serves to secure the power cord 12 in the handle. Point 23 is positioned to rigidly hold the nozzle 11 in a recess 50 which is molded into the shell halves.

The motor 15 is a small l 15 volt AC, 60 CPS shaded pole motor, such as is sold by the Jakel Electric Company under the Number 250-038-315, and is held in the body 10 cantilevered by standofi spacers. These spacers hold the motor 15 and the fan assembly 16 mounted on the motor shaft 30, rigidly in line with an air intake opening 19. To protect the operator this opening 19 is covered by a metal screen 35.

The fan assembly 16, shown in detail in FIG. 3, consists of a plurality of vanes 31, equidistantly spaced on a dish 34 around a raised hub 32. The hub 32 has a central opening 33 which is made of the size to fit shaft 30. A locking screw (not shown) passes through one wall of hub 32 and secures the assembly 16 into motor shaft 30. The assembly is molded in one piece, with each vane at an angle of 30from the diameter of the hub 32, out of the same type of material as the housing 10. Preferably the assembly 16 is dyed red in order to make the assembly more apparent to the user.

Nozzle 11 comprises a spaced pair of concentric stainless steel tubes 40 and 41, a resistor element 17, and an outer screen cap 42 which engages an exit screen 43. The entire nozle 11 is held in housing 10, in line withintake opening 19 3 by securing it in recess 50 by a screw 63 which passes through opening 23. Referring now to FIGS. 5 and6 for the interior tube arrangement, screw 63 also holds the resistor card 45 and the inner tube 40 in spaced relationship with the outer tube 41. A different screw 64 is passed through opening 46 to maintain the other end of the element 17 and the tubes in the same spaced relationship and further holds the outer screen cap 42 on the outer tube 41. Spacers 65, 66, 67, 68 are located around the screws 63 and 64 to assure that the element 17 is centrally located within tube 40. Other spacers 69 are welded on tube 40 to assure that the tube 40 is centrally located within the outer tube 41. r

The resistor element 17 consists of a stiff, flat card 45 preferably composed of a refractory, electrically insulative material such as mica or' ceramic around which is helically wound a spiral of resistance heating wire 44. The heating wire 44 is electrically connected by leads 47 and 48 through switch 18 to power cord 12.

Preferably the cord 12, switch 18, motor 15 and resistor element 17 are electrically coupled as shown in FIG. 4 to provide for heating or cooling of an object placed before exit screen 42. In FIG. 4 cord 12 is seen to consist of a hot line 50, a return 51 and ground lead 52 which is coupled to grounding terminal 53. The hot line 50 is coupled into the switch into terminals 54 and 55 while the return lead 51 is diverted through the fan motor 15 and the electrode structure 17 and thence to terminals 56 and 57 with the internal switch connections shown as elements 58 and 59. It should be noted that in FIG. 4 the switch is shown in the ofi' position. When the switch is in the ofi position, the gun may be connected to an appropriate source of electric power by means of plugging in the power lead 12 into a grounded outlet after which the switch 18 may be advanced to the cooling position which activates the blower and permits the gun by means of the fan 16 to pull air into the gun through intake 35 and expel it through outlet screen 43.

When the switch is advanced to element 17 is now activated and the gun expels hot air by passing the air taken in by intake screen 35 over the heated filament 44 and out through output screen 43. Upon activation of the heating element, the temperature of the air transmitted through output screen 43 reaches temperatures in excess of l,000 Fahrenheit within minutes.

Because these temperatures are capable of igniting some flammable substances and causing harmful burns and other efthe hot position the heating will stand not only high shock but also high temperature and which will not readily transmit heat from the nozzle 11. to the handle of the housing 10.

' Because at times it is desirable that the operator utilize both hands during the manipulation of the material to be treated with'the heated exhaust air, the gun is provided with separated ears 60 situated on the rear of housing above the intake orifice 35. These ears now maintain the housing 10 at orifice 35 a specified distance from any table top and permits the gun to be stably held away from a surface so that the nozzle is directed upward. These ears in conjunction with the rear point of handle 10, designated 61, acts as a tripod to hold the gun in this upright position and permits greater versatility of the gun without modifications or special structures to hold the gun.

The gun thus described in the present application is a modern design, lightweight, compact, quiet, manueverable, versatile, reliable, requiring little or no maintenance, permits fast and easy repair and is of significantly lower cost than the two provided in the market place.

Having now described the present invention, the inventor claims:

1. A portable heat gun comprising a hollow housing of high impact plastic generally having a pistol grip configuration containing a brushless self-lubricating electric motor, said motor carrying a fan in line with an intake orifice provided in the rear of said housing, said fan being designed to pull air through said intake orifice and to push said air past said motor past a spiraled resistance heating wire helically wound around a stiff, flat, refractory card of electrically insulative material said card mounted in line with said motor on the opposite 'side thereof from said intake orifice, and thence through an exhaust orifice, said exhaust orifice and said card being maintained in a first tubing co-axially maintained in a second tubing, said tubings and said card adapted to be maintained in spaced relationship to each other at one end in a recessed inset in said housing by spacer elements and a first screw passing through said tubings, said card, and the walls of said inset, thereby giving said gun the appearance of a pistol, a second screw passing through the other end of said tubings and said card with associated spacer elements, and means for transmitting electrical power from a power source through a three-way switch to said motor and said heating wire.

2. The heat gun of claim I wherein said switch can energize said motor without energizing said heating wire.

3. The heat gun of claim 1, wherein said fan pushes air between said tubings to prevent said tubings from equalizing in temperature.

4. A portable heat gun comprising a hollow housing of high impact plastic generally having a pistol grip configuration containing a brushless self-lubricating electric motor, said motor carrying a fan in line with an intake orifice provided in the rear of said housing, said fan being designed to pull air through said intake orifice and to push said air past said motor past an electn'cally heated resistor element mounted in line with said motor on the opposite side thereof from said intake orifice and through an exhaust orifice, said exhaust orifice and said element being maintained in a stainless steel tubing co-axially maintained in a second tubing, recessed inset in said housing thereby giving said gun the appearance of a pistol, said housing provided with a pair of projecting ears in the proximity of said intake orifice wherein said ears and the handle of said housing act as a tripod to hold said tubings in a vertical position, and means for transmitting electrical power from a power source through a three-way switch to said motor and said element.

5. A portable heat comprising a hollow housing of high impact plastic generally having a pistol grip configuration containing a brushless self-lubricating electric motor, said motor carrying a fan in line with an intake orifice provided in the rear of said housing, said fan being designed to pull air through said intake orifice and to push said air aHast said motor past a spiraled resistance heating wire hel1c y wound around a stiff,

flat, refractory card of electrically insulative materials,said said card mounted in line with said motor on the opposite side thereof from said intake orifice, and thence through an exhaust orifice, said exhaust orifice and said card being maintained in a first tubing co-axially maintained in a second tubing, said tubings and said card adapted to be maintained in space relationship to each other at one end in a recessed inset in said housing by spacer elements and a first screw passing through said tubings, said card, and walls of said inset, thereby giving said gun the appearance of a pistol, a second screw passing through the other end of said tubings and said card with associated spacer elements, support means projecting outwardly from said housing in the proximity and on both sides of said intake orifice whereby, when placed on a horizontal surface, said means and said handle act as a tripod to hold said tubings in a vertical position and to space said intake orifice from said level surface by a clearance sufiicient to readily allow for the pulling of air into said intake orifice, and means for transmitting electrical power from a power source through a three-way switch to said motor and said heating wire.

adapted to be maintained in a 

1. A portable heat gun comprising a hollow housing of high impact plastic generally having a pistol grip configuration containing a brushless self-lubricating electric motor, said motor carrying a fan in line with an intake orifice provided in the rear of said housing, said fan being designed to pull air through said intake orifice and to push said air past said motor past a spiraled resistance heating wire helically wound around a stiff, flat, refractory card of electrically insulative material said card mounted in line with said motor on the opposite side thereof from said intake orifice, and thence through an exhaust orifice, said exhaust orifice and said card being maintained in a first tubing co-axially maintained in a second tubing, said tubings and said card adapted to be maintained in spaced relationship to each other at one end in a recessed inset in said housing by spacer elements and a first screw passing through said tubings, said card, and The walls of said inset, thereby giving said gun the appearance of a pistol, a second screw passing through the other end of said tubings and said card with associated spacer elements, and means for transmitting electrical power from a power source through a three-way switch to said motor and said heating wire.
 2. The heat gun of claim 1 wherein said switch can energize said motor without energizing said heating wire.
 3. The heat gun of claim 1, wherein said fan pushes air between said tubings to prevent said tubings from equalizing in temperature.
 4. A portable heat gun comprising a hollow housing of high impact plastic generally having a pistol grip configuration containing a brushless self-lubricating electric motor, said motor carrying a fan in line with an intake orifice provided in the rear of said housing, said fan being designed to pull air through said intake orifice and to push said air past said motor past an electrically heated resistor element mounted in line with said motor on the opposite side thereof from said intake orifice and through an exhaust orifice, said exhaust orifice and said element being maintained in a stainless steel tubing co-axially maintained in a second tubing, adapted to be maintained in a recessed inset in said housing thereby giving said gun the appearance of a pistol, said housing provided with a pair of projecting ears in the proximity of said intake orifice wherein said ears and the handle of said housing act as a tripod to hold said tubings in a vertical position, and means for transmitting electrical power from a power source through a three-way switch to said motor and said element.
 5. A portable heat gun comprising a hollow housing of high impact plastic generally having a pistol grip configuration containing a brushless self-lubricating electric motor, said motor carrying a fan in line with an intake orifice provided in the rear of said housing, said fan being designed to pull air through said intake orifice and to push said air past said motor past a spiraled resistance heating wire helically wound around a stiff, flat, refractory card of electrically insulative materials,said said card mounted in line with said motor on the opposite side thereof from said intake orifice, and thence through an exhaust orifice, said exhaust orifice and said card being maintained in a first tubing co-axially maintained in a second tubing, said tubings and said card adapted to be maintained in space relationship to each other at one end in a recessed inset in said housing by spacer elements and a first screw passing through said tubings, said card, and walls of said inset, thereby giving said gun the appearance of a pistol, a second screw passing through the other end of said tubings and said card with associated spacer elements, support means projecting outwardly from said housing in the proximity and on both sides of said intake orifice whereby, when placed on a horizontal surface, said means and said handle act as a tripod to hold said tubings in a vertical position and to space said intake orifice from said level surface by a clearance sufficient to readily allow for the pulling of air into said intake orifice, and means for transmitting electrical power from a power source through a three-way switch to said motor and said heating wire. 